Bypass for a suspension damper

ABSTRACT

A vehicle suspension damper comprises a cylinder and a piston assembly including a damping piston along with working fluid within the cylinder. A bypass permits fluid to avoid dampening resistance of the damping piston. A fluid path through the bypass is controlled by a valve that is shifted by a piston surface when the contents of at least one predetermined volume is injected against the piston surface which acts upon the valve. In one embodiment, the bypass is remotely operable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation of theco-pending patent application, U.S. patent application Ser. No.14/154,857, filed on Jan. 14, 2014, entitled “BYPASS FOR A SUSPENSIONDAMPER”, by John Marking, Attorney Docket Number FOXF/0047USC1, andassigned to the assignee of the present invention, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

The U.S. patent application Ser. No. 14/154,857 is a continuationapplication of and claims the benefit of U.S. patent application Ser.No. 13/175,244, filed on Jul. 1, 2011 and is now issued U.S. Pat. No.8,627,932, entitled “BYPASS FOR A SUSPENSION DAMPER” by John Marking,with Attorney Docket No. FOXF/0047USP1, and assigned to the assignee ofthe present application, which is incorporated herein, in its entirety,by reference.

The U.S. patent application Ser. No. 13/175,244 claims priority to andbenefit of U.S. Provisional Patent Application 61/361,127 filed on Jul.2, 2010, entitled “BYPASS LOCK-OUT VALVE FOR A SUSPENSION DAMPER” byJohn Marking, with Attorney Docket No. FOXF/0047USL, which isincorporated herein, in its entirety, by reference.

The U.S. patent application Ser. No. 13/175,244 is acontinuation-in-part application of and claims the benefit of U.S.patent application Ser. No. 13/010,697, filed on Jan. 1, 2011 and is nowissued U.S. Pat. No. 8,857,580, entitled “REMOTELY OPERATED BYPASS FOR ASUSPENSION DAMPER” by John Marking, with Attorney Docket No.FOXF/0043USP1, and assigned to the assignee of the present application,which is incorporated herein, in its entirety, by reference.

The U.S. patent application Ser. No. 13/010,697 claims priority to andbenefit of U.S. Provisional Patent Application 61/296,826 filed on Jan.20, 2010, entitled “BYPASS LOCK-OUT VALVE FOR A SUSPENSION DAMPER” byJohn Marking, with Attorney Docket No. FOXF/0043USL which isincorporated herein, in its entirety, by reference.

The U.S. patent application Ser. No. 13/010,244 is acontinuation-in-part application of and benefit of U.S. patentapplication Ser. No. 12/684,072, filed on Jan. 7, 2010 and is nowabandoned, entitled “REMOTELY OPERATED BYPASS FOR A SUSPENSION DAMPER”by John Marking, with Attorney Docket No. FOXF/0032US, and assigned tothe assignee of the present application, which is incorporated herein,in its entirety, by reference.

The U.S. patent application Ser. No. 13/175,244 is acontinuation-in-part application of and claims the benefit of U.S.patent application Ser. No. 12/684,072, filed on Jan. 7, 2010 and is nowabandoned, entitled “REMOTELY OPERATED BYPASS FOR A SUSPENSION DAMPER”by John Marking, with Attorney Docket No. FOXF/0032US, and assigned tothe assignee of the present application, which is incorporated herein,in its entirety, by reference.

The U.S. patent application Ser. No. 12/684,072 claims priority to andbenefit of U.S. Provisional Patent Application 61/143,153 filed on Jan.7, 2009, entitled “REMOTE BYPASS LOCK-OUT” by John Marking, withAttorney Docket No. FOXF/0032L, which is incorporated herein, in itsentirety, by reference.

BACKGROUND Field of the Invention

Embodiments of the present invention generally relate to a damperassembly for a vehicle. More specifically, certain embodiments relate toa remotely operated bypass device used in conjunction with a vehicledamper.

Vehicle suspension systems typically include a spring component orcomponents and a dampening component or components. Typically,mechanical springs, like helical springs are used with some type ofviscous fluid-based dampening mechanism and the two are mountedfunctionally in parallel. In some instances features of the damper orspring are user-adjustable. What is needed is an improved method andapparatus for adjusting dampening characteristics, including remoteadjustment.

SUMMARY OF THE INVENTION

The invention includes a vehicle suspension damper comprising a cylinderand a piston assembly comprising a damping piston along with workingfluid within the cylinder. A bypass permits fluid to avoid dampeningresistance of the damping piston. A fluid path through the bypass iscontrolled by a valve that is shifted by a piston surface when thecontents of at least one predetermined volume is injected against thepiston surface which acts upon the valve. In one embodiment, the bypassis remotely operable.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features can be understoodin detail, a more particular description may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a section view showing a suspension damping unit with abypass.

FIG. 2 is an enlarged section view showing a valve of the bypass in aclosed position and showing a plurality of valve operating cylinders inselective communication with an annular piston surface of the valve.

FIG. 3 is a section view showing the valve in an open position due tofluid flow through the bypass.

FIG. 4 is a section view showing the valve in an open position after theannular piston surface of the valve has been moved by the injection offluid from a first valve operating cylinder.

FIG. 5 is a section view showing the valve in a locked-out position dueto fluid injected from the first and second operating cylinders.

FIG. 6 is a schematic diagram showing a control arrangement for aremotely operated bypass.

FIG. 7 is a schematic diagram showing another control arrangement for aremotely operated bypass.

FIG. 8 is a graph showing some operational characteristics of thearrangement of FIG. 7.

DETAILED DESCRIPTION

As used herein, the terms “down,” “up,” “downward,” “upward,” “lower,”“upper” and other directional references are relative and are used forreference only. FIG. 1 is a section view of a suspension damping unit100. The damper includes a cylinder portion 102 with a rod 107 and apiston 105. In one embodiment, the fluid meters from one side of thepiston 105 to the other side by passing through flow paths 110, 112formed in the piston 105. In the embodiment shown, shims 115, 116 areused to partially obstruct the flow paths 110, 112 in each direction. Byselecting shims 115, 116 having certain desired stiffnesscharacteristics, the dampening effects caused by the piston 105 can beincreased or decreased and dampening rates can be different between thecompression and rebound strokes of the piston 105. For example, shims115 are configured to meter rebound flow from the rebound portion 103 ofthe cylinder 102 to the compression portion 104 of the cylinder 102.Shims 116, on the other hand, are configured to meter compression flowfrom the compression portion of the cylinder to the rebound portion. Inone embodiment, shims 116 are not included on the rebound portion side,nor is there a compression flow path such as path 112, leaving thepiston essentially “locked out” in the compression stroke without somemeans of flow bypass. Note that piston apertures (not shown) may beincluded in planes other than those shown (e.g. other than aperturesused by paths 110 and 112) and further that such apertures may, or maynot, be subject to the shims 115, 116 as shown (because for example, theshims 115, 116 may be clover-shaped or have some other non-circularshape). In one embodiment, the piston is solid and all damping flow musttraverse a flow bypass and/or communicate with a reservoir.

A reservoir 125 is in fluid communication with the damper cylinder 102for receiving and supplying damping fluid as the piston rod 107 moves inand out of the cylinder 102. The reservoir includes a cylinder portion128 in fluid communication with the rebound portion 103 of the dampercylinder 102 via fluid conduit 129. The reservoir also includes afloating piston 130 with a volume of gas on a backside 131 (“blind end”side) of it, the gas being compressible as the reservoir cylinder 128,on the “frontside” 132 fills with damping fluid due to movement of thedamper rod 107 and piston 105 into the damper cylinder 102. Certainfeatures of reservoir type dampers are shown and described in U.S. Pat.No. 7,374,028, which is incorporated herein, in its entirety, byreference. The upper portion of the rod 107 is supplied with a bushingset 109 for connecting to a portion of a vehicle wheel suspensionlinkage. In another embodiment, not shown, the upper portion of the rod107 (opposite the piston) may be supplied with an eyelet to be mountedto one part of the vehicle, while the lower part of the housing shownwith an eyelet 108 is attached to another portion of the vehicle, suchas the frame, that moves independently of the first part. A springmember (not shown) is usually mounted to act between the same portionsof the vehicle as the damper. As the rod 107 and piston 105 move intocylinder 102 (during compression), the damping fluid slows the movementof the two portions of the vehicle relative to each other due, at leastin part, to the incompressible fluid moving through the shimmed paths112 (past shims 116) provided in the piston 105 and/or through a meteredbypass 150, as will be described herein. As the rod 107 and piston 105move out of the cylinder 102 (during extension or “rebound”) fluidmeters again through shimmed paths 110 and the flow rate andcorresponding rebound rate is controlled, at least in part, by the shims115.

In FIG. 1, the piston is shown at full extension and moving downward ina compression stroke, the movement shown by arrow 157. The bypass 150includes a tubular body 155 that communicates with the damper cylinder102 through entry 160 and exit 165 pathways. The bypass 150 permitsdamping fluid to travel from a first side of the piston 105 to the otherside without traversing shimmed flow paths 110, 112 that may otherwisebe traversed in a compression stroke of the damper. In FIG. 1, thebypass 150 is shown in an “open” position with the flow of fluid throughthe bypass shown by arrows 156 from a compression side to a rebound sideof the piston 105. In the embodiment of FIG. 1, the bypass 150 includesa remotely controllable, needle-type check valve/throttle valve 200,located proximate an exit pathway 165 allowing flow in direction 156 andchecking flow in opposite direction.

The entry pathway 160 to the bypass 150 in the embodiment shown in FIG.1 is located towards a lower end of the damper cylinder 102. In oneembodiment, as selected by design (e.g. axial location of entry 160),the bypass will not operate after the piston 105 passes the entrypathway 160 near the end of a compression stroke (or elsewhere in thestroke as desired). In one embodiment, this “position sensitive” featureensures increased dampening will be in effect near the end of thecompression stoke to help prevent the piston from approaching a“bottomed out” position (e.g. impact) in the cylinder 102. In someinstances, multiple bypasses are used with a single damper and the entrypathways for each may be staggered axially along the length of thedamper cylinder in order to provide an ever-increasing amount ofdampening (via less bypass) as the piston moves through its compressionstroke and towards the bottom of the damping cylinder. Each bypass mayinclude some or all of the features described herein. Certain bypassdamper features are described and shown in U.S. Pat. Nos. 6,296,092 and6,415,895, each of which are incorporated herein, in its entirety, byreference. Additionally, the bypass and valve of the present embodimentscan be used in any combination with the bypass valves shown anddescribed in co-pending U.S. patent application Ser. Nos. 12/684,072 and13/010,697.

FIGS. 2-5 are enlarged views showing the remotely operable needle valve200 in various positions. FIG. 2 shows the valve 200 in a closedposition (e.g. during a rebound stroke of the damper). The valveincludes a valve body 204 housing a movable piston 205 which is sealedwithin the body. The piston 205 includes a sealed chamber 207 adjacentan annularly-shaped piston surface 206 at a first end thereof. Thechamber 207 and piston surface 206 are in fluid communication with aport 225 accessed via opening 226. Two additional fluid communicationpoints are provided in the body including an inlet 202 and an outlet 203for fluid passing through the valve 200. Extending from a first end ofthe piston 205 is a shaft 210 having a cone-shaped valve member 212(other shapes such as spherical or flat, with corresponding seats, willalso work suitably well) disposed on an end thereof. The cone-shapedmember 212 is telescopically mounted relative to, and movable on, theshaft 210 and is biased toward an extended position due to a spring 215coaxially mounted on the shaft 210 between the member 212 and the piston205. Due to the spring biasing, the cone-shaped member 212 normallyseats itself against a seat 217 (as it is in FIG. 2) formed in aninterior of the body 204. As shown, the cone shaped member 212 is seatedagainst seat 217 due to the force of the spring 215 and absent anopposite force from fluid entering the valve along path 156 from thebypass (FIG. 1). As member 212 telescopes out, a gap 220 is formedbetween the end of the shaft 210 and an interior of member 212. A vent221 is provided to relieve any pressure formed in the gap. With a fluidpath through the valve (from 203 to 202) closed, fluid communication issubstantially shut off from the rebound side of the cylinder into thevalve body (and hence through the bypass back to the compression side)and its “dead-end” path is shown by arrow 219.

In one embodiment, there is a manual pre-load adjustment on the spring215 permitting a user to hand-load or un-load the spring using athreaded member 208 that transmits motion of the piston 205 towards andaway from the conical member, thereby changing the compression on thespring 215.

Also shown in FIG. 2 is a plurality of valve operating cylinders 251,252, 253. In one embodiment, the cylinders each include a predeterminedvolume of fluid 255 that is selectively movable in and out of eachcylindrical body through the action of a separate corresponding piston265 and rod 266 for each cylindrical body. A fluid path 270 runs betweeneach cylinder and port 225 of the valve body where annular pistonsurface 206 is exposed to the fluid. Because each cylinder has aspecific volume of substantially incompressible fluid and because thevolume of the sealed chamber 207 adjacent the annular piston surface 206is known, the fluid contents of each cylinder can be used, individually,sequentially or simultaneously to move the piston a specific distance,thereby effecting the dampening characteristics of the system in arelatively predetermined and precise way. While the cylinders 251-253can be operated in any fashion, in the embodiment shown each piston 265and rod 266 is individually operated by a solenoid 275 and eachsolenoid, in turn, is operable from a remote location of the vehicle,like a cab of a motor vehicle or even the handlebar area of a motor orbicycle (not shown). Electrical power to the solenoids 275 is availablefrom an existing power source of a vehicle or is supplied from its ownsource, such as on-board batteries. Because the cylinders may beoperated by battery or other electric power or even manually (e.g. bysyringe type plunger), there is no requirement that a so-equippedsuspension rely on any pressurized vehicle hydraulic system (e.g.steering, brakes) for operation. Further, because of the fixed volumeinteraction with the bypass valve there is no issue involved in steppingfrom hydraulic system pressure to desired suspension bypass operatingpressure.

FIG. 3 is a section view showing the valve of FIG. 2 in an open positiondue to fluid flow. In the damping-open position, fluid flow through thebypass 150 provides adequate force on the member 212 to urge itbackwards, at least partially loading the spring 215 and creating fluidpath 201 from the bypass 150 into a rebound area 103 of the dampercylinder 102. The characteristics of the spring 215 are typically chosento permit the valve 200 (e.g. member 212) to open at a predeterminedbypass pressure, with a predetermined amount of control pressure appliedto inlet 225, during a compression stroke of the damper 100. For a givenspring 215, higher control pressure at inlet 225 will result in higherbypass pressure required to open the valve 200 and correspondinglyhigher damping resistance in the bypass 150 (more compression dampingdue to that bypass). In one embodiment, the control pressure at inlet225 is raised high enough to effectively “lock” the bypass closedresulting in a substantially rigid compression damper (particularly truewhen a solid damping piston is also used).

In one embodiment, the valve is open in both directions when the valvemember 212 is “topped out” against valve body 204. In another embodimenthowever, when the valve piston 205 is abutted or “topped out” againstvalve body 204 the spring 215 and relative dimensions of the valve 200still allow for the cone member 212 to engage the valve seat 217 therebyclosing the valve. In such embodiment backflow from the rebound side ofthe cylinder 102 to the compression side is always substantially closedand cracking pressure from flow along path 156 is determined by thepre-compression in the spring 215. In such embodiment, additional fluidpressure may be added to the inlet through port 225 to increase thecracking pressure for flow along path 156 and thereby increasecompression damping through the bypass over that value provided by thespring compression “topped out.” It is generally noteworthy that whilethe descriptions herein often relate to compression damping bypass andrebound shut off, some or all of the bypass channels (or channel) on agiven suspension unit may be configured to allow rebound damping bypassand shut off or impede compression damping bypass.

FIG. 4 is a section view showing the valve 200 in an open position afterthe annular piston surface 206 of the valve has been moved by theinjection of fluid from a first valve operating cylinder 251. Like FIG.3, the valve 200 is also in a dampening-open position but the piston(and thus the spring 215) has been preloaded by the application of fluidto annular piston 206 from the first valve operating cylinder 251. As aresult the fluid flow through the bypass required to move member 212 isincreased. The valve operating cylinders 251-253 each include apredetermined, measured volume of fluid that is designed to cause thepiston to move a specific amount, each thereby loading the spring 215 aspecific known amount. For example, in FIG. 4 the first valve operatingcylinder 251 has been emptied into sealed chamber 207 where it has actedon annular piston surface 206 and translated the piston a predetermineddistance. The result is a further compression of the spring 215 therebyrequiring a greater fluid flow on conical member 212 to force to openthe bypass. The enlarged flow is illustrated by heavy arrow 201. Thecylinders are designed to each contain a fluid volume that will create adesired movement of the piston when their contents are injected into thevalve either alone or in combination. In one embodiment, for example,the cylinders are “plumbed” to operate in series and they can besequentially emptied to increase dampening in discrete stages. Theresult is an increase in dampening every time another cylinder emptiesits contents. Conversely, causing the fluid volumes to return to theirrespective cylinders ensures that piston will return a certain distance,reducing dampening in the circuit as more fluid is permitted to bypassthe effects of the piston shims.

In an example, when the valve 200 is in its normally closed position(shown in FIG. 2 with spring 215 relaxed), an area “behind” the annularpiston 205 has a 10 cc volume and is pre-filled with fluid. In order totranslate the piston 205 to a point where dampening is increased ameaningful amount, the piston must move “forward” a distance that addsan additional 5 cc in volume to sealed area 207. By sizing cylinder 251to hold a fluid volume of 5 cc, the piston 205 is ensured of movingforward to the desired position after the contents have been injectedbehind the annular piston surface 206.

In one embodiment, inlet 225 may be pressurized using one or more of thefluid cylinders 251-253 to shift the valve 200 to a third or“locked-out” position. FIG. 5 is a section view showing the valve 200 ina locked-out position due to fluid injected from the first and secondoperating cylinders 251, 252. Because the valve 200 is in a locked-outposition fluid is prevented from flowing through the bypass in eitherdirection regardless of compression or rebound stroke severity. Anactivating amount of fluid has been introduced via inlet 225 to act uponannular piston surface 206 and move the piston 205 and with it, member212 toward seat 217. As illustrated, sufficient activating fluid hasfully compressed the spring 215 (substantial stack out) thereby closingthe cone member 212 against the seat 217 and sealing the bypass to bothcompression flow and rebound flow. In the embodiment shown, the valve200 can be shifted to the third, locked-out position from either thefirst, closed position of FIG. 2 or the second, open position of FIG. 3,depending upon the operator cylinder or cylinders chosen and the fluidvolume of those cylinders.

Note that when in the “locked out” position, the valve 200 as shown willopen to compression flow if and when the compression flow pressureacting over the surface area of the seated valve cone member 212 exceedsthe inlet 225 pressure acting over the surface area of the annularpiston surface 206 (unless the cone member and valve assembly aremechanically “stacked out” such as by the mechanical screw adjuster).Such inlet 225 pressure is determined by the pistons, rods and solenoidsthat provide the force responsible for moving fluid between theoperating cylinders and the closed area 207. Such pressure may beselected to correspond therefore to a desired compression overpressurerelief value or “blow off” value thereby allowing compression bypassunder “extreme” conditions even when the bypass is “locked out”.

In the embodiment illustrated, the valve 200 is intended to be shiftedto the locked-out position with control fluid acting upon annular pistonsurface 206 of piston 205. In one embodiment, the activating fluid viainlet 225 is sized so that the valve 200 is closed to rebound fluid(with the cone-shaped member 212 in seat 217) but with the spring 215not fully compressed or stacked out. In such a position, a high enoughcompression force (e.g. compression flow) will still open the valve 200and allow fluid to pass through the valve in a compression stroke. Inone arrangement, the activating pressure, controlled remotely, may beadjusted between levels where the lock-out is not energized and levelswhere the lock-out is fully energized. The activating fluid may also beprovided at intermediate levels to create more or less dampingresistance through the bypass. Note that other separate damping valves(e.g. shims or pressure differential operated) may be added in thebypass channel generally to alter bypass damping characteristics inncompression or rebound or both. The various levels are possible bysizing, and in some cases combining the cylinders.

FIG. 6 is a schematic diagram showing a control arrangement 400 for aremotely operated bypass. As illustrated, a signal line 416 runs from aswitch 415 to any number of valve operating cylinders 410 which in turn,operate a bypass valve 200 via fluid path 405. While FIG. 6 issimplified and involves control of a single bypass valve 200, it will beunderstood that any number of valves and groups of control cylinderscould be operated simultaneously or separately depending upon needs in avehicular suspension system. Additional switches could permit individualoperation of separate damper bypass valves.

A remotely operable bypass like the one described above is particularlyuseful with an on-/off-road vehicle. These vehicles can have as morethan 20″ of shock absorber travel to permit them to negotiate rough,uneven terrain at speed with usable shock absorbing function. Inoff-road applications, compliant dampening is necessary as the vehiclerelies on its long travel suspension when encountering often largeoff-road obstacles. Operating a vehicle with very compliant, long travelsuspension on a smooth road at higher speeds can be problematic due tothe springiness/sponginess of the suspension and corresponding vehiclehandling problems associated with that (e.g. turning roll, brakingpitch). Such compliance can cause reduced handling characteristics andeven loss of control. Such control issues can be pronounced whencornering at high speed as a compliant, long travel vehicle may tend toroll excessively. Similarly, such a vehicle may pitch and yawexcessively during braking and acceleration. With the remotely operatedbypass dampening and “lock out” described herein, dampeningcharacteristics of a shock absorber can be completely changed from acompliantly dampened “springy” arrangement to a highly dampened and“stiffer” (or fully locked out) system ideal for higher speeds on asmooth road. In one embodiment, where compression flow through thepiston is completely blocked, closure of the bypass 150 results insubstantial “lock out” of the suspension (the suspension is renderedessentially rigid). In one embodiment, where some compression flow isallowed through the piston (e.g. port 112 and shims 116), closure of thebypass 150 (closure of valve 200) results in a stiffer but stillfunctional compression damper. In one embodiment, some of the bypasschannels, of for example a shock having multiple bypass channels, havingcorresponding compression flow entries located “deeper” in thecompression stroke are locked out (or restricted) while bypass channelshaving entries “higher” in the stroke are left open. That results in along travel shock absorber being functionally converted to a muchshorter travel shock absorber for, in one example, on highway use (inthe short travel mode). Such a short travel mode is further advantageousin that it allows for elimination of undesired travel from the end ofthe stroke as opposed to causing a shortening of the damper. As such,the ride height of a so equipped vehicle is unaffected by travel modeadjustment from long to short. In one embodiment, the shims 116 aresized, to optimize damping when the bypass 150 is open and when bypass150 is closed based on total anticipated driving conditions. In one

FIG. 7 illustrates, for example, a system 500 including three variables:rod speed, rod position and vehicle speed. Any or all of the variablesshown may be considered by logic unit 502 in controlling the solenoidsof the valve operating cylinders 251-253. Any other suitable vehicleoperation variable may be used in addition to or in lieu of thevariables 515, 505, 510 such as, for example, piston rod compressionstrain, eyelet strain, vehicle mounted accelerometer (ortilt/inclinometer) data or any other suitable vehicle or componentperformance data. In one embodiment, piston 105's position withincylinder 102 is determined using an accelerometer to sense modalresonance of cylinder 102. Such resonance will change depending on theposition of the piston 105 and an on-board processor (computer) iscalibrated to correlate resonance with axial position. In oneembodiment, a suitable proximity sensor or linear coil transducer orother electro-magnetic transducer is incorporated in the dampeningcylinder to provide a sensor to monitor the position and/or speed of thepiston (and suitable magnetic tag) with respect to the cylinder. In oneembodiment, the magnetic transducer includes a waveguide and a magnet,such as a doughnut (toroidal) magnet that is joined to the cylinder andoriented such that the magnetic field generated by the magnet passesthrough the piston rod and the waveguide. Electric pulses are applied tothe waveguide from a pulse generator that provides a stream of electricpulses, each of which is also provided to a signal processing circuitfor timing purposes. When the electric pulse is applied to thewaveguide, a magnetic field is formed surrounding the waveguide.Interaction of this field with the magnetic field from the magnet causesa torsional strain wave pulse to be launched in the waveguide in bothdirections away from the magnet. A coil assembly and sensing tape isjoined to the waveguide. The strain wave causes a dynamic effect in thepermeability of the sensing tape which is biased with a permanentmagnetic field by the magnet. The dynamic effect in the magnetic fieldof the coil assembly due to the strain wave pulse, results in an outputsignal from the coil assembly that is provided to the signal processingcircuit along signal lines. By comparing the time of application of aparticular electric pulse and a time of return of a sonic torsionalstrain wave pulse back along the waveguide, the signal processingcircuit can calculate a distance of the magnet from the coil assembly orthe relative velocity between the waveguide and the magnet. The signalprocessing circuit provides an output signal, either digital or analog,proportional to the calculated distance and/or velocity. Atransducer-operated arrangement for measuring rod speed and velocity isdescribed in U.S. Pat. No. 5,952,823 and that patent is incorporated byreference herein in its entirety.

While a transducer assembly located at the damper measures rod speed andlocation, a separate wheel speed transducer for sensing the rotationalspeed of a wheel about an axle includes housing fixed to the axle andcontaining therein, for example, two permanent magnets. In oneembodiment, the magnets are arranged such that an elongated pole piececommonly abuts first surfaces of each of the magnets, such surfacesbeing of like polarity. Two inductive coils having flux-conductive coresaxially passing therethrough abut each of the magnets on second surfacesthereof, the second surfaces of the magnets again being of like polaritywith respect to each other and of opposite polarity with respect to thefirst surfaces. Wheel speed transducers are described in U.S. Pat. No.3,986,118 which is incorporated herein by reference in its entirety.

In one embodiment, as illustrated in FIG. 7, the logic unit 502 withuser-definable settings receives inputs from the rod speed 510 andlocation 505 transducers as well as the wheel speed transducer 515. Thelogic unit 502 is user-programmable and depending on the needs of theoperator, the unit records the variables and then if certain criteriaare met, the logic circuit sends its own signal to the bypass to eitherclose or open (or optionally throttle) the bypass valve 200. Thereafter,the condition of the bypass valve is relayed back to the logic unit 502.

FIG. 8 is a graph that illustrates a possible operation of oneembodiment of the bypass system 500 of FIG. 7. The graph assumes aconstant vehicle speed. For a given vehicle speed, rod position is shownon a y axis and rod velocity is shown on an x axis. The graphillustrates the possible on/off conditions of the bypass at combinationsof relative rod position and relative rod velocity. For example, it maybe desired that the bypass is operable (bypass “on”) unless the rod isnear its compressed position and/or the rod velocity is relatively high(such as is exemplified in FIG. 7). The on/off configurations of FIG. 7are by way of example only and any other suitable on/off logic based onthe variable shown or other suitable variables may be used. In oneembodiment, it is desirable that the damper become relatively stiff atrelatively low rod velocities and low rod compressive strain(corresponding for example to vehicle roll, pitch or yaw) but remainscompliant in other positions. In one embodiment, the piston rod 107includes a “blow off” (overpressure relief valve typically allowingoverpressure flow from the compression side to the rebound side) valvepositioned in a channel coaxially disposed though the rod 107 andcommunicating one side of the piston (and cylinder) with the other sideof the piston (and cylinder) independently of the apertures 110,112 andthe bypass 150.

In one embodiment, the logic shown in FIG. 7 assumes a single damper butthe logic circuit is usable with any number of dampers or groups ofdampers. For instance, the dampers on one side of the vehicle can beacted upon while the vehicles other dampers remain unaffected.

While the examples illustrated relate to manual operation and automatedoperation based upon specific parameters, the remotely operated bypass150 can be used in a variety of ways with many different driving androad variables. In one example, the bypass 150 is controlled based uponvehicle speed in conjunction with the angular location of the vehicle'ssteering wheel. In this manner, by sensing the steering wheel turnseverity (angle of rotation), additional dampening can be applied to onedamper or one set of dampers on one side of the vehicle (suitable forexample to mitigate cornering roll) in the event of a sharp turn at arelatively high speed. In another example, a transducer, such as anaccelerometer, measures other aspects of the vehicle's suspensionsystem, like axle force and/or moments applied to various parts of thevehicle, like steering tie rods, and directs change to the bypass valvepositioning in response thereto. In another example, the bypass can becontrolled at least in part by a pressure transducer measuring pressurein a vehicle tire and adding dampening characteristics to some or all ofthe wheels in the event of, for example, an increased or decreasedpressure reading. In one embodiment, the damper bypass or bypasses arecontrolled in response to braking pressure (as measured, for example, bya brake pedal sensor or brake fluid pressure sensor or accelerometer).In still another example, a parameter might include a gyroscopicmechanism that monitors vehicle trajectory and identifies a “spin-out”or other loss of control condition and adds and/or reduces dampening tosome or all of the vehicle's dampers in the event of a loss of controlto help the operator of the vehicle to regain control.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed:
 1. A vehicle suspension damper comprising: a cylinderand a piston assembly comprising a piston; a working fluid within saidcylinder; a bypass having a fluid pathway between a first and secondsides of the piston; a valve for controlling the flow of fluid throughthe bypass, the valve including a displaceable valve closing memberhaving a piston surface on one side thereof, the piston surface biasingthe valve towards a closed position when displaced; a biasing memberbiasing the piston towards the closed position, the displaced pistonsurface and biasing member operable in conjunction to urge the valveclosing member towards the closed position; and at least twopredetermined fluid volumes in selective communication with the pistonsurface for causing displacement thereof; wherein each predeterminedvolume comprises a valve operating cylinder, the fluid contents of thecylinder injectable into the valve to displace the piston surface andwherein the valve operating cylinders are substantially equal.